Biometric Factors in the VRF-G Formula for IOL Power Calculation

To assess the contribution of each optional parameter to the IOL power calculation and evaluate the effect of omitting biometric variables (ACD, LT, WTW) using the VRF-G formula.

A total of 501 eyes from 501 consecutive patients included in the study underwent cataract surgery with in-the-bag implantation of one-piece soft hydrophobic acrylic posterior chamber IOLs, AcrySof IQ SN60WF (Alcon Labs, Fort Worth, TX, USA). The primary calculation comprised five measured variables, and IOL power was recalculated for different combinations of omitting ACD, LT, and WTW. Outcome measurements included the difference in IOL power calculations between different omission combinations.

Omitting any of the biometric variables resulted in a significant difference in the mean difference in IOL power calculation (ranging from 0.029 to 0.108 diopters), except for WTW omission alone (0.002 diopters). ACD proved to have the most impact, with its omission resulting in larger differences in power calculations (range: 0.177-0.248 diopters) compared to combinations where ACD was not omitted (range: 0.057-0.141 diopters). The shortest eyes were most affected by ACD omission.

The study highlights the importance of ACD in IOL power calculations, particularly for shorter eyes. WTW and LT were found to be less important when using the VRF-G formula for IOL power calculations.